Federal environmental pollution standards and some state standards limit the amount of gasoline vapors that may be allowed to escape into the atmosphere during filling of a gasoline tank for a vehicle. In an empty gas tank which is being filled with gasoline, the vapors that are in the tank are driven out as liquid gasoline is pumped into the tank. California standards require as a minimum that at least ninety five percent (95%) of the vapors exhausted from a gasoline tank as it is being filled are recovered and kept from escaping into the atmosphere.
In one system currently under use in California, a collapsible bellows surrounds all but a small portion of the outlet end of a dispenser nozzle and in use seals against the exterior flange of a fill pipe. The bellows thus creates a sealed cavity between the outside of the nozzle and the end of the fill pipe to form a closed system. As gasoline is pumped into the tank from the nozzle, the vapors driven out of the tank are sucked into a vapor recovery line extending through the dispenser and leading to a remote storage vessel. The vapors enter the recovery line through inlet ports spaced from the end of the discharge opening of the nozzle. With this type of system, the collection of vapors is done on a one-to-one volumetric relationship with one volume of vapor being recovered for each volume of gasoline dispensed into the tank.
Use of the foregoing described nozzle bellows arrangement is difficult for some. In modern gasoline powered vehicles, a restricter plate is mounted in the fill pipe and includes a small port through which the end of the nozzle must fit before gasoline can be dispensed. The bellows conceals the end of the nozzle once in the fill pipe making it hard to align the nozzle with the small port. Moreover, before fuel may be dispensed from the nozzle, a seal must have been made with the end of the bellows against the flange of the fill pipe. The bellows is spring loaded so that some force is required in order to effect the seal. This force also must be maintained while the fuel is being dispensed into the tank. Thus, for those dispensers requiring hands on operation, a customer must continuously push inwardly against the dispenser to maintain the seal while also depressing the trigger of the dispenser. For those fuel dispensers which include an automatic trigger lock, a retainer mechanism on the nozzle is designed to latch with the inside edge of the fill pipe flange and may be utilized to hold the bellows in place against the end of the fill pipe. Manipulation of this locking feature and the push-pull nature of its release can be difficult. One example of the foregoing general type of dispenser is shown in U.S. Pat. No. 4,276,916. Another patent disclosing the use of a bellows to seal between the body of a dispenser nozzle and the end of a fill pipe is disclosed in U.S. Pat. No. 4,306,594.
In another form of vapor recovery system which does not utilize a bellows seal, both air and gasoline vapors are collected from the fill pipe in a volumetric amount in excess of the volume of liquid gasoline which is pumped into the vehicle gasoline tank. With such an arrangement, it is important to the storage of fuel vapors that the amount of air being included with the fuel vapors be kept to a minimum to avoid building pressure in the underground storage tank. In some vehicles, the construction of gasoline tanks is such that a vent pipe from within the tank is opened in the fill pipe upstream of the restricter port permitting the flow of air to mix with gasoline vapors and a possible reduction of the recovered volume of gasoline vapors.
The prior art also includes a splash guard which is mounted on the dispenser nozzle and merely serves to protect a customer against gasoline splashing. One form of prior art splash guard includes an elastomeric disc curved in a shape so as to deflect gasoline back toward the fill pipe. This disc shaped form of splash guard, however, is not intended to nor does it function to limit the escape of gasoline vapors into the atmosphere.